The present invention relates generally to the field of protective relaying, and more particularly to a xe2x80x9csynch checkxe2x80x9d algorithm for determining when to close a circuit breaker.
When both sides of an open circuit breaker are energized, caution must be taken so that, when the breaker closes, the two power systems can be tied together in a safe manner. This tying of power systems is called synchronization.
The synchronous check protective function measures the voltage magnitude, voltage phase angle, and power system frequency differences across an open circuit breaker. When all three of these parameters are within an acceptable level, the close command is issued, or permitted to be issued, in an attempt to close the circuit breaker. Circuit breakers do not close instantaneously. A typical breaker closing time is between 2 to 10 cycles (or 8-40 xc2xc-cycles). A goal of the present invention is to provide an improved algorithm for determining the optimal time to permit the breaker to close.
This invention utilizes a mechanism that averages a buffer of anticipated optimal closing times to provide for a more accurate method of determining when to issue a breaker close signal. This is used in a Breaker Close Time feature of performing synchronism checking in the electrical power industry (for example, in a generator protection device). Other features of the invention are described below.